Study On The Correlation Between γ - Aminobutyric Acid Receptor And Mouse Oocyte Maturation

Objective In this experiment, we investigated the expression of γ-aminobutyric acid(GABA) and A receptor subunits in oocytes and its surrounding cumulus cells of the mouse, and explored the role of during ovarian folicular development and oocyte maturation.Methods Immature female Kunming mice were treated with Pregnant Mare Serum Gonadotropin(PMSG) to induce the follicular development, with PMSG/human Chorionic Gonadotropin(h CG) to promote the ovulation. First, we measured the transcriptomic level of GABAA receptor subunits in oocytes and its surrounding cumulus cells by q RT-PCR. Second, Western blotting and Immunofluorescence technique were used to detect the expression of the α5 in cumulus cells isolated from oocytes according to oocyte nuclear maturity. The expression and localization of GABA in the germinal(GV) vesicle and metaphase Ⅱ(MⅡ) cumulus cells surrouding oocytes were evaluated by immunohistochemical analysis.Results GABA-A receptor subunits have different transcriptional level in mouse cumulus cells at different nuclear maturation stage(GV and MⅡ). Comparing the CCs isolated from oocytes at GV(CCGV) with the MⅡ groups(CCMⅡ), we found the expression levels of α5, β3 were up regulated in the CCMⅡ groups(P<0.05). But the relative m RNA abundance of α3, δ, π were down regulated in the CCGV groups compared to in those CCMⅡ groups and θ expression level exhibited no significant difference in CCGV and CCMⅡ groups(P<0.05). The transcriptional level of α4 m RNA is absent in the CCMⅡ group, but its m RNA is present in CCGV group. By Western blotting and Immunofluorescence technique, α5 were high expressed in the MⅡ cumulus cells surrouding oocytes than in those at GV stage(P<0.05). The GABA was observed to express in the GV and MⅡ cumulus cells from mouse oocytes by immunohistochemical analysis.Conclusion We found that GABAA receptor subunits exhibited differential transcriptional levels in mouse cumulus cells at different oocyte nuclear maturity stages. The expression of γ-aminobutyric acid and A receptor subunits in cumulus cells of the mouse indicates that GABA and A receptor subunits may participate in the regulation of ovarian follicular development and oocyte maturation.